#17613: merge with 3.3.

Lib/idlelib/ColorDelegator.py

@@ -51,6 +51,10 @@ class ColorDelegator(Delegator):
             self.config_colors()
             self.bind("<<toggle-auto-coloring>>", self.toggle_colorize_event)
             self.notify_range("1.0", "end")
+        else:
+            # No delegate - stop any colorizing
+            self.stop_colorizing = True
+            self.allow_colorizing = False
 
     def config_colors(self):
         for tag, cnf in self.tagdefs.items():

Misc/NEWS

@@ -1015,6 +1015,8 @@ _ Issue #17385: Fix quadratic behavior in threading.Condition.  The FIFO
 IDLE
 ----
 
+- Issue #17613: Prevent traceback when removing syntax colorizer in IDLE.
+
 - Issue #1207589: Backwards-compatibility patch for right-click menu in IDLE.
 
 - Issue #16887: IDLE now accepts Cancel in tabify/untabify dialog box.